Transmission power control method of uplink packet data transmission

ABSTRACT

A mobile station (MS) transmits a first data flow to a first group of base stations with a first power offset, transmits a second data flow to a second group of base stations, and further transmits a pilot signal. A radio network controller (RNC) controls the power of the pilot signal power based on reception errors of the second data flow, calculates the first power offset based on signaled required level of the first power offset from base stations (BTS) of the first group which calculate the required level of the first power offset based on an occurrence of retransmission, signals the calculated first power offset to the mobile station.

TECHNICAL FIELD

This invention is related to uplink data packet transmission in widebandcode division multiple access (WCDMA) technology. Furthermore, inparticular, this invention is closely related to enhancement of uplinkdedicated transport channel (EUDCH). Aiming to improve the transmissionefficiency of uplink packet, the EUDCH includes new base stationfunctions such as fast retransmission and scheduling of uplink datapacket data.

BACKGROUND ART

In a WCDMA system, the radio network controller (RNC) controls the datarate of uplink packet data transmission for a multiplicity of mobilestations (MS). The radio network controller scheduling of the uplinkdata rate can be combined with base station (BTS) scheduling in order toachieve better radio link efficiency and therefore higher systemcapacity. One example of this combination of the RNC and BTS packetscheduling is the so-called Enhanced Dedicated Channel (EUDCH). We referhere 3GPP TR 25.896 V1.2.1 (2004-01), Technical Report of 3GPP (3rdGeneration Partnership Project).

In addition to packet scheduling capability at a base station, EUDCHconsiders a base station to have ARQ (automatic retransmission)capability in order to request retransmission of an erroneous datapacket directly to the mobile station without the involvement of theradio network controller. Generally, BTS ARQ is much faster than RNCARQ, hence the former outperforms the latter in terms of its requireddelay for retransmission.

When a mobile station has multiple uplink data flows, it is possible touse a different scheduling method for the different data flow dependingon the requirement of the flow. For example, if the BTS scheduling isoptimized for mainly a best-effort service while a voice call servicecan be better controlled by the RNC scheduling, the mobile station isable to transmit multiple data flows using appropriate scheduling modeto meet the requirement of each data flow.

FIG. 1 gives an illustration of a system with the BTS/RNC scheduling andARQ. Three types of mobile stations (MS1 to MS3) 101 to 103 in a cellare connected to base station (BTS) 104 which is controlled by radionetwork controller (RNC) 105. Two mobile stations (MS2, MS3) 102, 103,which are denoted as “BtsSch,” are BTS scheduled mobile stations whiletwo mobile stations (MS1, MS3) 101, 103, which are denoted as “RncSch,”are scheduled by radio network controller 105. Note that MS3 103 has twodata flows and each flow has a different scheduling mode, i.e., BtsSchand RncSch. In other words, MS3 103 has two uplink data flows while eachof MS1 101 and MS2 102 has one uplink data flow. Hence the data rate ofMS2 102 and the data rate of the first flow of MS3 103 are controlled bybase station 104 while radio network controller 105 controls the datarate of MS1 101 and the data rate of the second flow of MS3 103.Similarly, the retransmission of MS2 102 and the retransmission of thefirst flow of MS3 103 are requested by the base station while the radionetwork controller controls the retransmission of MS1 101 and theretransmission of the second flow of MS3 103. It is important to notethat MS1 101 is connected to both base stations 104, 104A at the sametime and radio network controller 105 combines received data packetsfrom two base stations 104, 104A.

When a mobile station transmits two data packet flows using both the BTSand RNC scheduling simultaneously, assuming the user is making a voicecall while sending a multimedia message, the transmission power of twodata flows should be appropriately controlled. In the example of theaforementioned EUDCH, the transmission power of two data flows, denotedby DCH (dedicated channel) and EUDCH (enhanced dedicated channel), canbe conventionally controlled in the following manner:P _(cch)(t)=P _(cch)(t−1)+Δ_(cch)(t)P _(dch)(t)=PO _(DCH) P _(cch)(t)P _(eudch)(t)=PO _(EUDCH) P _(cch)(t)  (1)where PO_(DCH) and P_(dck)(t) are the transmission power offset andtransmission power at time t of DCH (RNC scheduled data flow) whilePO_(EUDCH) and P_(eudch)(t) are those of EUDCH (BTS scheduled dataflow). The power offsets of DCH and EUDCH are controlled in asemi-static manner by the radio network controller while thetransmission power of pilot signal P_(cch)(t) is controlled by bothinner and outer loop control. More specifically, Δ_(cch)(t) composes ofinner and outer loop adjustment factors. We refer both adjustmentalgorithms included in 3GPP TS 25.214 V5.6.0 (2003-09), Technical Reportof 3GPP (3rd Generation Partnership Project).

The literatures cited in this description will be listed below:

[1] 3GPP TR 25.896 V1.2.1 (2004-01) Technical Report 3rd GenerationPartnership Project; Technical Specification Group Radio Access Network;Feasibility Study for Enhanced Uplink for UTRA FDD; (Release 6)

[2] 3GPP TS 25.214 V5.6.0 (2003-09) Technical Report 3rd GenerationPartnership Project; Technical Specification Group Radio Access Network;Physical layer procedures (FDD) (Release 5)

DISCLOSURE OF THE INVENTION Problems to be Solved by the Invention

When the base station level ARQ is enabled, the control of thetransmission power shown in Equation (1) has the following problems tobe solved:

(1) Interaction of Power Control and BTS ARQ:

When a base station controls an ARQ process, the radio networkcontroller should set an appropriate power offset for a BTS schedulingdata packet (EUDCH data flow). If the power offset is set too large, avery low error probability can occur so that there is no benefit ofhaving the base station level ARQ processing. If the power offset is settoo low, a large error probability would increase the total latency ofthe uplink data packet transmission. To make this problem moredifficult, if the data packet frame lengths of DCH and EUDCH aredifferent, the radio network controller should also anticipate adifference in interleaving gain of DCH and EUDCH. For example, if themoving speed of the mobile station changes randomly in time, so does theinterleaving gain of DCH and EUDCH.

(2) Interaction of Power Control and Soft Handover in Uplink:

The transmission power control for DCH and EUDCH data flows shouldenable high link efficiency even when there is a difference of softhandover gain of DCH and EUDCH. For example, when a DCH data flow isreceived by two base stations while only one base station receives anEUDCH data flow, the transmission power control should control thetransmission power of both DCH and EUDCH in a “simultaneously efficient”way. If it optimizes for only either one of DCH and EUDCH, the linkquality on the other channel would degrade. To make the problem moredifficult, the number of base stations receiving the DCH and EUDCH dataflows changes randomly and frequently as the mobile station moves aroundthe network.

The object of the present invention is to provide a transmission powercontrol method which can simultaneously achieve efficient transmissionof each of a plurality of data flows.

Means for Solving Problem

According to the first aspect of the invention, a method of controllingtransmission power in a mobile communication system which has aplurality of mobile stations, a plurality of base stations, and a radionetwork controller includes the steps of: a mobile station transmittinga first data flow to a base station of a first group with a first poweroffset to a pilot signal, and transmitting a second data flow to a basestation of a second group; the base station of the first groupcontrolling retransmission of the first data flow, calculating requiredlevel of the first power offset based on an occurrence ofretransmission, and signaling the required level to the radio networkcontroller; the base station of the second group receiving the seconddata flow, and sending the received second data flow to the radionetwork controller; the radio network controller combining the seconddata flow sent from the base station of the second group, controllingthe pilot signal power based on a reception error of the second dataflow, calculating the first power offset based on the signaled requiredlevel of the first power offset, and signaling the calculated firstpower offset to the mobile station; and the mobile station updating thefirst power offset to the signaled first power offset.

According to the second aspect of the invention, a method of controllingtransmission power in a mobile communication system which has aplurality of mobile stations, a plurality of base stations, and a radionetwork controller includes the steps of: the mobile stationtransmitting a first data flow to a base station of a first group with afirst power offset to a pilot signal, and transmitting a second dataflow to a base station of a second group; the base station of the firstgroup controlling retransmission of the first data flow, calculatingrequired level of the first power offset based on a target error rate ofthe first data flow, and signaling the required level to the radionetwork controller; the base station of the second group receiving thesecond data flow, and sending the received second data flow to the radionetwork controller; the radio network controller combining the seconddata flow sent from the base station of the second group, controllingthe pilot signal power based on a target error rate of the second dataflow, receiving the required level of the first power offset from thebase station of the first group, calculating the first power offsetbased on the signaled required level of the first power offset inresponse to the required level of the first power offset from aresponsible base station, increasing the power offset based on highpriority or high delay sensitivity of the first data flow, signaling thecalculated first power offset to the mobile station, and signaling thecalculated first power offset to the base station of the first group;and the mobile station updating the first power offset to the signaledfirst power offset, wherein the responsible base station for the mobilestation is a base station in the first group receiving the first dataflow correctly, and most frequently, than other base stations in thegroup.

According to the third aspect of the invention, a method of controllingtransmission power in a mobile communication system which has aplurality of mobile stations, a plurality of base stations, and a radionetwork controller, includes the steps of: a mobile station transmittinga first data flow to a bas station of a first group with a first poweroffset to a pilot signal, transmitting a second data flow to a basestation of a second group, and transmitting, in addition to the firstdata flow, a third data flow to the first group with a second poweroffset to the pilot signal; the mobile station choosing transmission ofeither first or third data flow in a time interval but notsimultaneously together; the base station of the first group controllingretransmission of both the first data flow and the third data flow,separately calculating required level of the first and second poweroffsets based on an occurrence of retransmission of the first and thirddata flows, respectively, and signaling the two required levels to theradio network controller; the base station of the second group receivingthe second data flow, and sending the received second data flow to theradio network controller; the radio network controller combining thesecond data flow sent from the base station of the second group,controlling the pilot signal power based on a reception error of thesecond data flow, calculating the first and second power offsets basedon the signaled required levels of the first and second power offsets,respectively, and signaling the calculated first and second poweroffsets to the mobile station; the mobile station updating the first andsecond power offsets to the signaled first and second power offsets,respectively.

According to the fourth aspect of the invention, a method of controllingtransmission power in a mobile communication system which has aplurality of mobile stations, a plurality of base stations, and a radionetwork control station, includes the steps of: a mobile stationtransmitting a first data flow to base station of a first group,transmitting a second data flow to a base station of a second group, andtransmitting a pilot signal; determining a transmission power of thefirst data flow by using a first power offset to the pilot signal;setting the first power offset in accordance with retransmission statusof the first data flow at the base station of the first group; notifyinga corresponding mobile station of the first power offset that has beenset; and controlling a transmission power of the pilot signal so thatreception quality at the base station of the second group comes to aprescribed target quality.

Advantageous Effect of the Invention

The present invention solves the problem related to fast change of adifference in the interleaving gain between two data flows due to adifferent frame length of two flows. When two data flows have adifferent frame length, the conventional technique allow to adjust thetransmission power of both flows only optimized for either one of thedata flows hence inefficient for the other flow. The present inventionadjusts the transmission power of each data flow, simultaneously, tomeet efficiency of respective data flows. This benefit is explained inFIG. 2, using an example of an EUDCH system, that the transmission powerof an EDH data flow is controlled based on the reception status at theradio network controller while the transmission power of the EUDCH dataflow is controlled based on the reception status at the base station.

In addition, the present invention solves the problem related to fastchange of difference in macro-diversity gain between two data flows dueto a different number of receiving base stations of two flows. When twodata flows have a different number of the receiving base stations, theconventional technique allow only to adjust the transmission power ofboth flows only optimized for either one of the data flows henceinefficient for the other flow. According to the present invention, thetransmission power of each data flow is adjusted simultaneously to meetefficiency of respective data flow. This benefit is explained in FIG. 2and FIG. 5 described later, using an example of the EUDCH system. Thetransmission power of the EDH data flow is controlled based on thecombined reception status at the radio network controller, afterreceiving the DCH data flow by a group of base stations, while thetransmission power of the EUDCH data flow is controlled based on thereception status at the second group of base stations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram illustrating a system with RNC scheduling andBTS scheduling uplink data packet transmission.

FIG. 2 is a block diagram illustrating a system according to anembodiment of the present invention.

FIG. 3 is a flow chart of the base station procedure of calculating arequired power offset.

FIG. 4 is a flow chart of the base station procedure of sending therequired power offset.

FIG. 5 is a flow chart of the radio network controller procedure ofassigning a new power offset.

FIG. 6 is a block diagram illustrating a system according to anotherembodiment of the present invention.

DESCRIPTION OF THE REFERENCE NUMERALS

10, 101, 102, 103 Mobile station (MS)

20, 104, 104A Base station (BTS)

30, 105 Radio network controller (RNC)

201 CCH pilot transmitter

202 DCH data frame transmitter

203, 601, 602 EUDCH data frame transmitter

204, 603 Power offset controller

205 Inner loop power controller

206, 207, 605 ARQ transmitter

208 Data frame demultiplexer

209 Pilot signal receiver

210 DCH frame decoder

211, 606 EUDCH frame decoder

212 Downlink TPC command generator

213, 215, 609 ARQ receiver for EUDCH data frame

214, 607, 608 Power offset estimator

216 Outer loop TPC controller

217 DCH frame receiver

218 EUDCH frame receiver

219, 610 Radio resource controller

604 Time multiplexer

BEST MODE FOR CARRYING OUT THE INVENTION

FIG. 2 illustrates one possible realization of the system according tothe present invention including RNC/BTS ARQ and transmission powercontrol. As an example, aforementioned EUDCH is considered and theillustrated system comprises one mobile station (MS) 10, one basestation (BTS) 20 and one radio network controller (RNC) 30.

Mobile station 10 is provided with CCH pilot transmitter (CCH Tx) 201,DCH data frame transmitter (DCH Tx) 202, EUDCH data frame transmitter(EDCH Tx) 203, power offset controller (PO) 204, inner loop powercontroller (IL IPC) 205, ARQ transmitter (ARQ Tx) 206 for EUDCH dataframe, and ARQ transmitter (ARQ Tx) 207 for DCH data frame. The mobilestation transmits the common pilot signal CCH generated by transmitter201, the RNC scheduled DCH data flow generated by transmitter 202, andthe BTS scheduled EUDCH data flow generated by transmitter 203.Respective power offsets of each flow are controlled by power offsetcontroller 204 and these data flows are combined as a transmissionsignal of mobile station 10. Inner loop power controller 205 controlsthe total transmission power of mobile station 10 (see Equation (1)).Uplink data transmission 221 between mobile station 10 and base station20 is established.

Base station 20 is provided with data frame demultiplexer (DEMUX) 208,pilot signal receiver (CCH Rx) 209, DCH frame decoder (DCH DEC) 210,EUDCH frame decoder (EDCH DEC) 211, downlink TPC command generator (TPC)212, ARQ receiver (ARQ Rx) 213 for EUDCH data frame, and power offsetestimator (POE) 214.

Radio network controller 30 is provided with ARQ receiver (ARQ Rx) 215for DCH data frame, outer loop TPC controller (OL TPC) 216, DCH framereceiver (DCH Rx) 217, EUDCH frame receiver (EDCH Rx) 218, and radioresource controller (RRC) 219.

The base station receives both transmitted data flows and demultiplexesthem into separate processing chains by demultiplexer 208. Firstly, CCHis decoded by decoder 209 and processed by downlink TPC commandgenerator 212, which generates power control commands (downlink TPCcommands) 220. Commands 220 are sent to inner loop power controller 212in mobile station 10. The RNC scheduled DCH flow is decoded by decoder210, and decoded RNC scheduled DCH flow 224 is then forwarded to radionetwork control unit 217 at radio network controller 30 via a BTS-RNCinterface. The retransmission controller, i.e., ARQ receiver 215, atradio network controller 30 requests erroneous DCH data packets backfrom the mobile station by notifying ARQ transmitter 207 at mobilestation 10. Also, the reception status of DCH is used by outer looppower controller 216, which controls the target signal-to-noise ratio(SIR) 223 of the base station power controller, i.e., TPC commandgenerator 212, via a control signaling interface. The decoding of theBTS scheduled EUDCH data packet is performed by EUDCH decoder 211, anddecoded EUDCH data frame 225 is forwarded to EUDCH frame receiver 218 atradio network controller 30. EUDCH decoder 211 forwards the receptionstatus of EUDCH to the retransmission slave controller, i.e., ARQreceiver 213, located in base station 10. ARQ receiver 213 communicateswith the retransmission master controller, i.e., ARQ transmitter 206, atmobile station 10 as illustrated by downlink ARQ feedback 222. Forfurther details of the system shown in FIG. 2, we refer 3GPP TR 25.896V1.2.1 (2004-01) and 3GPP TS 25.214 V5.6.0 (2003-09). It should be notedthat it is possible to dispose power offset estimator (POE) 214 in radionetwork controller 30 instead of disposing it in base station 20.

The following is a detail description of a process performed in poweroffset estimator 214 in base station 20. FIG. 3 is a flow chartillustrating the description presented in the following. In the Figure,“TarBler”, “DelAck” and “DelNack” represent a target error rate, apositive adjustment factor for the power offset, and a negativeadjustment factor for the power offset, respectively. “DelAnack”,“AccDel”, “RecPO” and “AssPO” represent an adjustment factor, anaccumulated adjustment factor, a required power offset, and an assignedpower offset, respectively. “K31” is a given value of DelAck and “K32”is a maximum allowed power offset.

Initially, in step 301, the target error rate of the EUDCH data flow isset as well as an adjustment factor for the power offsets. Theadjustment factor should be sufficiently large to guarantee fastconvergence of the adjustment. After the EUDCH data packet is decoded bythe base station, at step 302, a required power offset is adjusted bythe reception status of the data packet, at steps 303, 304, 305 and 306.This adjustment is accumulated over a period of time and the requiredpower offset is calculated as follows, at steps 306, 307, 308:$\begin{matrix}{{PO}_{REC} = {\min( {{{PO}_{EDCH} + {\sum\limits_{t \in T_{MSR}}{\Delta_{anck}(t)}}},{PO}_{MAX}} )}} & (2)\end{matrix}$

The PO_(REC) is the calculated required power offset of EUDCH duringmeasurement period T_(MSR). The measurement duration and the maximumupper limit of power offset PO_(MAX) are predefined by the radio networkcontroller. The maximum upper limit PO_(MAX) guarantees a defineddynamic range of the power offset for the EUDCH data flow. Furthermore,the adjustment term Δ_(anck) is decided based on of the reception statusof EUDCH such that: $\begin{matrix}{{\Delta_{anck}(t)} = \{ \begin{matrix}{\Delta_{ACK}\quad{if}\quad{successful}\quad{transmission}\quad({ACK})} \\{{- \Delta_{NACK}}\quad{if}\quad{not}\quad{successful}\quad{transmission}\quad({NACK})}\end{matrix} } & (3)\end{matrix}$

Note that the adjustment in Equation 2 can be selectively performed. Forexample, if there is no data reception or there is retransmission attime t, then Δ_(anck)(t)=0. The adjustment parameters, Δ_(ACK) andΔ_(NACK), can be defined by the following equation:(1−P _(nack)) Δ_(ACK) =P _(nack) Δ_(NACK)  (4)where P_(nack) is the target block error rate (BLER).

After the base station performs the power offset estimation proceduredescribe above, it, then, reports the calculated required power offsetto the radio network controller, at step 309.

Concretely, power offset estimator 214 forwards reported power offset227 to radio resource controller 219 which signals the power offset topower offset controller 204 in mobile station 10 as indicated by arrow226. If the assigned power offset is set in the radio networkcontroller, the base station reads the assigned power offset from theradio network controller, at step 310. Then the control of proceduregoes back to step 302.

Although the frequent reporting of the required power offset to theradio network controller is beneficial, its associated signalingoverhead can be significant. To reduce the signalling overhead, anevent-driven signaling is described in the following. FIG. 4 illustratesa detail example of the event-driven signaling procedure. In FIG. 4,“DiffPO” represents a difference of the power offsets, and “K41” is athreshold for the power offset reporting.

After the calculation of the required power offset is carried out atstep 401, the base station calculates a difference between thecalculated power offset and the assigned power offset, at step 402. Ifthe difference is greater than a predefined reporting threshold, basestation 20 sends the calculated power offset to radio network controller30, at step 403.log₁₀ |PO _(RNC) −PO _(REC) |>PO _(REPTH)  (5)where PO_(RNC) and PO_(REC) are the current and required power offsetsrespectively while PO_(REPTH) is a threshold for the power offsetreporting. The predefined reporting threshold can be signaled from theradio network controller to the base station.

From the method described so far, the radio network controller can havereporting from a base station on the required power offset of the EUDCHdata flow. From this recommendation from the base station, the radionetwork controller can decide a new power offset of the EUDCH data flow.A detail procedure of the radio network controller assigning the newpower offset is described in what follows:

A flow chart of this radio network controller procedure is given in FIG.5. Firstly, the radio network controller receives a required poweroffset from a group of base stations receiving the EUDCH data flow, atstep 501, and calculates a difference between the newly required poweroffset and the currently assigned power offset, at step 502. Then theradio network controller checks, at step 503, whether the required poweroffset is sent by a responsible base station (serving base station)which receives EUDCH data packets most frequently than other basestations. If not the responsible base station, the radio networkcontroller rejects the reported required power offset, at step 508. Ifthe power offset is sent by the responsible base station, the radionetwork controller checks whether the required power offset is smallerthan the currently assigned power offset, at step 504. If so, the radionetwork controller accepts the recommendation and sends the newlyassigned power offset to the base stations, at steps 505, 509. If not,the radio network controller accept the recommendation if the data flowis a high priority flow or delay sensitive, at steps 506, 507.Otherwise, the radio network controller rejects the required poweroffset, at step 508.

In the method described in FIG. 5, the radio network controller isutilizing priority and delay sensitivity of data flow when it decides toincrease the required power offset. The benefit associated with thisprocedure is that limited total radio resource is prioritized to servethe high priority flow or delay sensitive flow rather than the lowpriority best-effort flow.

Furthermore in the method described in FIG. 5, the radio networkcontroller accepts the required power offset only from the responsiblebase station. The benefit of this procedure is to minimize the requiredpower offset by selecting the best quality base station hence increasingcapacity of the uplink packet transmission.

Next, another embodiment of the present invention will be described. Asan example, aforementioned EUDCH is considered hereafter. FIG. 6illustrates another possible realization of the system according to thepresent invention. This illustrated system is an extension of theprevious realization of system shown in FIG. 2. The difference betweentwo systems are explained in the following:

There are two EUDCH data flows in addition to one DCH data flow. Theprevious system in FIG. 2 has only one EUDCH data flow. Therefore, thesystem in FIG. 6 is an extended system for the case when there are morethan one EUDCH data flows transmitted in an uplink. Each EUDCH data flowmay have different requirement on a target error rate due to differentQuality of Service (QoS) requirement. To support different QoS for eachdata flow, in this system, the transmitted data packet from each dataflow is separately encoded.

Therefore, mobile station 10 shown in FIG. 6 is provided with two EUDCHdata transmitters (EDCH1 Tx, EDCH2 Tx) 601, 602 and time multiplexer(SW) 604 for two data flows. The base station is provided with two poweroffset estimators (POE1, POE2) 607, 608.

Separate power offsets for two EUDCH data flows are used in power offsetcontroller 603 for a DCH data flow and two EUDCH data flows. Instead ofusing a common power offset for both EUDCH data flows, in thisembodiment, the separate power offsets are used in order to control thetarget error rate of each EUDCH data flow separately. Hence controllingseparate QoS of each EUDCH data flow is possible by use of the separatepower offset for each flow.

Time multiplexing is used for transmitting two EUDCH data flows. Theswitching at time multiplexer 604 is performing selection fortransmission from two data flows. For example, switching can performround robin selection from between two data flows when both flows havesufficient data waiting for transmission, in order to separately controlthe target error rate of each data flow.

Based upon receiving the transmitted EUDCH, data flow, base station 20performs decoding of the EUDCH data flow at EUDCH decoder 606.Successfully decoded data is forwarded to RNC 30 and the receptionstatus of the data flow is reported to power offset estimators 607, 608.As described above, there are two separate power offset estimators 607,608 in the base station for each EUDCH data flow. Hence the receptionstatus of the EUDCH data flow is updated to the corresponding poweroffset estimator only. For example, if the base station receives thefirst EUDCH data flow, the power offset estimator updating the poweroffset of the first EUDCH data flow will calculate new level of therequired power offset using the reception status. The calculation iscarried out by the same procedure illustrated in FIG. 3.

Both base station 20 and mobile station 10 are controllingretransmission of data flow by a master controller, i.e., ARQtransmitter 605, and a slave controller, i.e., ARQ receiver 609. ARQtransmitter 605 functions as a retransmission master controller at themobile station handling both EUDCH data flows, and ARQ receiver 609functions as a retransmission slave controller at the base stationhandling both EUDCH data flows. To support separate retransmission oftwo EUDCH data flow, retransmission information consists of thereception status and a corresponding data flow identification. Theidentification can be sent explicitly or it can be reduced implicitlyfrom fixed timing between the uplink data transmission and the downlinkcontrol data transmission.

The separate power offsets for two EUDCH data flows calculated by thebase station are reported to RNC radio resource controller 610. Based onthe reported power offset, RNC 30 makes decision on the power offset ofeach EUDCH data flow in a same way explained in FIG. 5. For example, iftwo EUDCH data flows have different priority and base station 20 reportsa higher power offset for both data flows, then RNC can increase onlythe power offset of the higher priority data flow while rejecting thatof the lower priority one. Then, RNC signals the newly assigned poweroffsets to the mobile station and base station(s).

Key aspect of the proposed realization in FIG. 6 is to employ twoseparate closed control loops for each EUDCH data flow. The base stationcalculates the required power offset for each data flow separately, itreports the power offsets to the radio network controller separately,and then the radio network controller makes the decision on new poweroffsets also separately. This separate closed loop power offset controlenables the separate control of QoS of each data flow hence the dataflow with high priority, for example, can be guaranteed more uplinkpower than that of lower priority. Note that this proposed system can bealso extended for a case of more than two EUDCH data flows.

1. A method of controlling transmission power in a mobile communicationsystem which comprises a plurality of mobile stations, a plurality ofbase stations, and a radio network controller, said method comprisingthe steps of: a mobile station transmitting a first data flow to a basestation of a first group with a first power offset to a pilot signal,and transmitting a second data flow to a base station of a second group;said base station of said first group controlling retransmission of saidfirst data flow, calculating required level of said first power offsetbased on an occurrence of retransmission, and signaling said requiredlevel to said radio network controller; said base station of said secondgroup receiving the second data flow, and sending the received seconddata flow to said radio network controller; said radio networkcontroller combining the second data flow sent from said base station ofsaid second group, controlling said pilot signal power based on areception error of said second data flow, calculating said first poweroffset based on said signaled required level of the first power offset,and signaling said calculated first power offset to said mobile station;and said mobile station updating the first power offset to said signaledfirst power offset.
 2. The method according to claim 1, wherein saidbase station of said first group calculates said required level of saidfirst power offset based on a target error rate of said first data flow.3. The method according to claim 1, wherein said radio networkcontroller controls said pilot signal power based on a target error rateof said second data flow.
 4. The method according to claim 1, whereinsaid radio network controller: receives said required level of firstpower offset from the base station of said first group; selects aresponsible (serving) base station for said mobile station from saidfirst group so that said responsible base station receives said firstdata flow correctly, and most frequently, than other base stations insaid group; and in response to required level of said first power offsetfrom said responsible base station, calculates said first power offset.5. The method according to claim 1, wherein said radio networkcontroller increases said power offset based on high priority or highdelay sensitivity of said first data flow.
 6. The method according toclaim 1, wherein said radio network controller signals said calculatedfirst power offset to the base station of said first group.
 7. Themethod according to claim 1 or 6, wherein the base station of said firstgroup sends, by a event-triggering manner, said required power offset,said method further comprising the steps of: initially, said radionetwork controller setting a reporting threshold; continuously, saidbase station of said first group calculating a difference between saidrequired power offset and said signaled power offset; and said basestation of said first group reporting said required power offset bydetecting that said difference becomes larger than said reportingthreshold.
 8. A method of controlling transmission power in a mobilecommunication system which comprises a plurality of mobile stations, aplurality of base stations, and a radio network controller, said methodcomprising the steps of: said mobile station transmitting a first dataflow to a base station of a first group with a first power offset to apilot signal, and transmitting a second data flow to a base station of asecond group; said base station of said first group controllingretransmission of said first data flow, calculating required level ofsaid first power offset based on a target error rate of said first dataflow, and signaling said required level to said radio networkcontroller; said base station of said second group receiving the seconddata flow, and sending the received second data flow to said radionetwork controller; said radio network controller combining the seconddata flow sent from the base station of said second group, controllingsaid pilot signal power based on a target error rate of said second dataflow, receiving said required level of the first power offset from thebase station of said first group, calculating the first power offsetbased on said signaled required level of the first power offset inresponse to the required level of said first power offset from aresponsible base station, increasing said power offset based on highpriority or high delay sensitivity of said first data flow, signalingsaid calculated first power offset to said mobile station, and signalingsaid calculated first power offset to the base station of said firstgroup; and said mobile station updating the first power offset to saidsignaled first power offset, wherein said responsible base station forsaid mobile station is a base station in said first group receiving saidfirst data flow correctly, and most frequently, than other base stationsin said group.
 9. The method according to claim 1, wherein said mobilestation controls power of said second data flow so that receptionquality of said pilot signal comes to prescribed target quality.
 10. Amethod of controlling transmission power in a mobile communicationsystem which comprises a plurality of mobile stations, a plurality ofbase stations, and a radio network controller, said method comprisingthe step of: a mobile station transmitting a first data flow to basestation of a first group with a first power offset to a pilot signal,transmitting a second data flow to a base station of a second group, andtransmitting, in addition to said first data flow, a third data flow tosaid first group with a second power offset to said pilot signal; saidmobile station choosing transmission of either first or third data flowin a time interval but not simultaneously together; said base station ofsaid first group controlling retransmission of both said first data flowand said third data flow, separately calculating required level of saidfirst and second power offsets based on an occurrence of retransmissionof said first and third data flows, respectively, and signaling said tworequired levels to said radio network controller; said base station ofsaid second group receiving the second data flow, and sending thereceived second data flow to said radio network controller; said radionetwork controller combining the second data flow sent from said basestation of said second group, controlling said pilot signal power basedon a reception error of said second data flow, calculating said firstand second power offsets based on said signaled required levels of thefirst and second power offsets, respectively, and signaling saidcalculated first and second power offsets to said mobile station; andsaid mobile station updating the first and second power offsets to saidsignaled first and second power offsets, respectively.
 11. The methodaccording to claim 10, wherein said first data flow and said third dataflow have distinct Quality of Service (QoS).
 12. The method according toclaim 11, wherein the Quality of Service includes priority and delaysensitivity.
 13. A method of controlling transmission power in a mobilecommunication system which comprises a plurality of mobile stations, aplurality of base stations, and a radio network control station, saidmethod comprising the step of: a mobile station transmitting a firstdata flow to a base station of a first group, transmitting a second dataflow to a base station of a second group, and transmitting the pilotsignal; determining a transmission power of said first data flow byusing a first power offset to a pilot signal; setting said first poweroffset in accordance with retransmission status of said first data flowat the base station of said first group; notifying a correspondingmobile station of said first power offset that has been set; andcontrolling a transmission power of said pilot signal so that receptionquality at the base station of said second group comes to a prescribedtarget quality.
 14. The method according to claim 13, wherein, in saidstep of setting said first power offset, said first power offset is setin accordance with a ratio of incorrect reception of said first dataflow.
 15. The method according to claim 13, wherein, in said step ofcontrolling a transmission power of said pilot signal, said targetquality is controlled so that an error rate of said second data flowcomes to a prescribed error rate.